The glass industry is an ancient industry; and because so much glass has been used for centuries, this industry was one of the first to mechanize. The discrete parts glass-forming machines have been made by several different companies, but basically they all imitate the centuries old hand forming of glassware merely mechanizing the various steps in the process. Since the discrete parts industry is essentially a process of intermittent motions, yet motions which must be inter-related, the typical individual section machine was one which was powered by pneumatic motors controlled by a multipart valve block. The valve block, in turn, was controlled by a timing drum driven from a line shaft which synchronized all parts of the entire machine.
The glass melting and delivery is to a glass feeder which feeds gobs of molten glass. In the individual section glassware-forming machines a gob distributor distributes these gobs successively in a predetermined order to the different individual sections of the machine. Each section of the machine is capable of independently producing glassware, and the sections of the machine then place such formed glassware on a take-off conveyor. Since the take-off conveyor must have room to accept the formed glassware, it is run at a suitable speed, and the various sections of the machine are operated in the predetermined sequence at a particular phase difference. In a six-section machine, this phase difference would be 60.degree..
The prior art discrete glassware-forming industry had a productivity percentage of about 40 to 85 percent. By this is meant the number of finished glassware products which passed inspection and which were packaged relative to the number of gobs being cut by the glass feeder was only in the range of 40 to 85 percent. Since glass has the lowest raw material cost and about the highest labor cost of any basic industry, any decrease in the labor content per finished piece makes the product increasingly salable in traditional markets and opens new markets for such glassware products.
Discrete glass-forming machines are started with all glass from the glass feeder being diverted down the cullet chute. This is to maintain uniform glass flow in the delivery section. Next, each individual machine section is brought onto the line. In the prior art this was done by actuating a mechanical clutch or the like so that that machine section started only in its proper phase position. The gob distributor was started to feed the gob to that particular machine section. In a six-section machine, for example, only one of six gobs would be fed to the respective section at start-up and the other five gobs would be diverted down the cullet chute.
In order to get that one machine section properly operating the operator had to set "on" and "off" buttons in a plurality of slots around the periphery of a rotating timing drum for that machine section. Typically, each individual machine section had 21 slots for these buttons which actuated on and off a main valve in turn directing air flow to operate pneumatic motors or actuators for the individual section. Before the timing drum was started, these buttons would be loosened with a wrench, moved to the approximate degree point, and then tightened. However, once the machine was started, the rotating timing drum was a particularly dangerous part of the machine. The operator had to adjust these buttons while they were moving and often only about 90.degree. to 120.degree. of the periphery of the timing drum was available to the operator for this adjustment. A maximum speed for the operation of the timing drum was about 20 RPM for smaller pieces of glassware being formed, so in this case the operator would have only about one second of time to loosen the stop button, try to move it a few degrees and then retighten it, during the available sector of adjustment. Many fingers have been lost by operators who miscalculated the amount of time available for this adjustment. This shows that the degree of resolution which the operator was able to achieve often was only about 3.degree. to 10.degree., depending on the speed of the drum. A further consideration was the safety of the operator while trying to adjust moving machinery. The U.S. Government has become increasingly concerned with the safety of personnel in manufacturing plants, and this manual of operation of the repositioning of the on and off buttons on the timing drum is causing increased scrutiny by the safety inspectors.
In order to adjust the speed of movement of the various machine parts, the operator had available to him a needle valve which could be manually adjusted, e.g., by a screwdriver slot. This controlled the velocity of air flow in the pneumatic actuator, and hence, controlled the speed of movement of the machine part. Again, this was something which was often adjusted while the machine was in operation in order that the operator could try to accomplish precise velocity control of the machine parts.
Once the operator had all the machine sections in operation, he then tried to speed up the entire machine by increasing the rotational speed of the line shaft, he might then find that he did not have sufficient time for a particular timed travel of a machine element. One reason was because gravity acted on the gobs and parisons with the same force regardless of speed. Another reason is because the heat in the glass had a shorter time in which to be dissipated. He would thus have to readjust the on and off buttons on the rotating timing drum for particular ones of the twenty-one functions for the main valves or have to readjust the needle valves for velocity control. This was not only a safety hazard but was subject to the many variables of human control and was a prime reason why the total productivity of the individual section glassware-forming machine was only about 40 to 85 percent.
The typical I.S. glass machine uses large amounts of cooling air to cool the molds and the glassware at various stages. This cooling air is ambient air which varies in temperature from winter to summer. This is one further reason why continual changes in the settings were required by the operator in order to try to maintain high productivity.